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By Suzann C. Ambrosio

Crude petroleum, the only commercially exploited mineral resource in Cameroon, continued to dominate developments in the mineral industry sector. International mining concerns have expressed interest in developing Cameroon's bauxite and iron and steel potentials. Domestically, the mineral industry focused on production of fertilisers for agricultural development, infrastructure construction, and hydrocarbon development, through the nearly self-sufficient production of fertilizer materials, cement, and crude oil. The mineral sector contributed 5.6% to the estimated 1981 gross domestic product (GDP) of $6.5 billion.2 Petroleum exports accounted for approximately 4.5% of the 1981 GDP and exceeded coffee and cocoa exports for the second consecutive year. The trade gap widened during the fiscal year ending on July 80, 1981, owing to a 21% increase in exports and a 25% increase in imports. Offsetting these balance-of-payments difficulties, typical of developing countries' early economic stages, were increases in foreign exchange reserves to $71 trillion by May 1983.

Jan 1, 1983

By Harry Dobroski, Larry G. Stolarczyk

Medium-frequency (MF) techniques have been successfully .[pplied] to the problem of radio voice communications in both coal and metal and nonmental mines. Long range is achieved by taking advantage of existing mine conductors that carry and propagate the signal over vast areas. It is very likely that in the near future such systems will become the referred method for general mine communications. MF techniques can also be applied to the areas of in-mine control and monitoring. Preliminary work in this area is described. In a western mine, locomotives are being operated under MF remote control in a loading operation. In several eastern mines, MF has been evaluated as a method for monitoring the status of devices in remote areas of the mines. All control and monitor information uses existing mine conductors.

By F. W. Hoertel

The Bureau of Mines investigated the use of depleted uranium as a sacrificial anode for the cathodic protection of submerged and underground structures of iron , steel , and copper . Uranium-metal couples were tested in simulated marine environments of varying oxygen contents at pH values between 5.5 and 8.5 and under simulated boiler service condition in Rolla , Mo. , city water . Similar couples were tested in samples of Missouri soils to simulate underground service . Uranium remained anodic to iron , steel , and copper in the simulated marine environments and under simulated boiler service if the electrolyte was oxygen- free city water . Uranium appeared to offer limited protection to iron , low- carbon steel , stainless steel , copper , and zinc in the simulated underground tests . Uranium anodes offer a space advantage because 1 cubic inch of uranium gives approximately the same protection as 2 cubic inches of magnesium or 1-1 /2 cubic inches of zinc .

Jan 1, 1963

Minerals are a fundamental component of the Nation" material and economic base. Without a continuous supply of minerals to meet growing and changing needs, the basic character of our society would be very different. The importance of minerals to the United States was reemphasized by the Congress in I970 when it enacted the Mining and Minerals Policy Act, which stated that it is the continuing policy of the Federal Government in the national interest to foster and encourage private enterprise in (I) the development of economically sound and stable domestic mining, minerals, metal and mineral reclamation industries, (2) the orderly and economic development of domestic mineral resources, reserves, and reclamation of metals and minerals to help assure satisfaction of industrial, security and environmental needs, (3) mining, mineral, and metallurgical research, including the use and recycling of scrap to promote the wise and efficient use of our natural and reclaimable mineral recources, and (4) the study and development of methods for the disposal, control, and reclamation of mineral waste products, and the reclamation of mined land, so as to lessen any adverse impact of mineral extraction and processing upon the physical environment that may result from mining or mineral activities.,.

Jan 1, 1977

By R. K. Koch

In seeking substitutes for such critical metals as chromium, cobalt, and nickel, the Bureau of Mines investigated techniques for shape-casting titanium in rammed sand molds. Castings were made in olivine, garnet, chromite, and, for comparison, zircon. It was found that commercial-grade castings up to 31 lb (maximum capacity of furnace) could be made in zircon or olivine molds if a zirconia mold wash was used. Castings up to 4 lb could be made in chromite molds, but heavier castings suffered from some mold-metal reaction. Garnet molds were found to be unsatisfactory for castings of all sizes because of gas blows and rough surfaces. In other tests shell castings of acceptable quality were produced in water-glass-bonded zircon and olivine molds up to weights of 8 lb, but chromite molds were unsatisfactory because rough casting surfaces were caused by mold-metal reaction. Unlike the currently used commercial processes, neither the rammed-sand nor the shell-molding processes developed by the Bureau of Mines generate noxious fumes at any step.

Jan 1, 1980

By Sabri Ergun

The method of constant compositions involves the determination of the time required for the attainment of a given conversion at various temperatures. Heretofore, it has been used in evaluating the energy of activation only. A development of the method, made in the present study, makes possible the evaluation of the functional dependence upon composition and the frequency factor in addition to the energy of activation. INTRODUCTION Kinetics of reactions are best analyzed in the light of the mechanism, energy requirements, and forces involved in the reaction. Such physico-chemical information is not often available in solid state phase transformations. The reaction rates are followed by changes in a physical property during the course of the reaction, and repeating the experiment at different temperatures permits the determination of activation energy only. The possibility of a complete kinetic analysis by such a purely "phenomenological" approach has been questioned.4/ In this report a method is developed making possible the evaluation of the functional dependence upon composition and frequency factor in addition to the energy of activation. The application of the method to a study of solid state order-disorder changes is demonstrated.

Jan 1, 1960

By L. J. Froisland

The Bureau of Mines conducted a 4-year research program at Uravan, Colo., on a 2-1/2-acre reclamation plot on the slope of a uranium tailings pile that had been covered with mine waste rock. The purpose of this study was to determine the effects of plant species, type of irrigation, type of fertilizers, and use of dust control chemicals on plant growth and surface coverage. Best grass coverage, nearly 100 percent with 240 plants per square foot, was developed in a section that was seeded with crested wheatgrass, fertilized with sewage sludge, and sprinkler irrigated. For comparison, a section that had been treated with commercial fertilizers developed 3.1 crested wheatgrass plants per square foot and 24 percent coverage without irrigation, and 8 plants per square foot and 75 percent coverage with irrigation. Results of spraying a dust control chemical were inconclusive. Russian-thistle invaded all test sections and ranged in density from 0.6 to 7.3 plants per square foot.

Jan 1, 1982

By E. D. Calvert

As part of its goal to minimize the requirements for critical and strategic minerals, the Bureau of Mines is conducting research to foster the use of domestically abundant materials such as molybdenum. This report describes the development of an investment shell molding technique that can be used to make castings of molybdenum and its alloys. The mold material is cubic Zr02 with a monoclinic Zr02 binder. The shell, formed by standard investment molding techniques described in the text, is prepared for molybdenum casting by firing for 6 hours at 1,550° C (2,822° F) or for 4 hours at 1,650° C (3,002° F). The resulting castings have predictable and reproducible dimensions with good detail. As-cast strength is poorer than the strength of wrought materials below 1,600° F. At and above this temperature, tensile strengths of cast and wrought materials are nearly equal. Aqueous corrosion of the castings in most media is insignificant.

Jan 1, 1982

By P. W. Jerant

The methane emissions from an advancing coal mine section were continuously monitored for 120 days. During this time, the section advanced 2,000 feet into virgin Pittsburgh coalbed producing 54,565 tons of coal with a total methane emission of 91 million ft3. Analysis of the data gathered showed that daily methane emissions did not correlate with overburden thickness and daily coal production. A good correlation was found between the daily methane emission and the average length of rib exposed to virgin coal.

Jan 1, 1976

By T. J. Ballard

"The Hog Creek mine, in lot 92 of the 17th district in Towns County, Georgia, was examined in 1890 by F. P. King, who reported the existence there of a 4-foot vein of corundum. The mine is about 2 miles west of Hiawassee, on the southern side of Ramey Mountain. Ed Burch, of Hog Creek, holds the surface rights, and the mineral rights appear to be vested in the heirs of William R. McConnell, who formerly owned and prospected the property.Examination by the Bureau of Mines showed the workings to be caved, but it was thought advisable to open the mine and uncover the reported vein. The Bureau's work consisted, of trenching and cleaning out the pits and shaft.William R. McConnell, the former owner, prospected the property in about 1890. At some tine during that operation, the prospect was visited by Francis P. Kings a geologist with the Georgia Geological Survey.3/King reported that a 4-foot vein of corundum was exposed g feet below the surface in the main cut and was opened for 20 feet along the strike. He also reported that the so-called ""Georgia rubies"" were taken from this mine.The main mine is about 2,000 feet- north of Hoc Creek on a timbered southern slope of Ramey Mountain. It lies at an altitude of about 2,100 feet, approximately 100 feet above the high-water level of the Catuga reservoir, which floods Hog Creek to a quarter of a mile above its confluence with the Hiawassee River. The nearest water is a small branch about 1,000 feet to the west.Chlorite schist is the principal host rock. It has been intruded by irregular masses of a very herd periodtite rock possibly troctolite. The schist near the surface is extremely weathered, presenting white and red laminations parallel to the schistosity. At a depth of 40 feet in the cross-cut it appears as a fine-grained green-chlorite schist. The schist strikes about N. 350 E. and dips 800 to the southeast.No corundum vein was found, and if any existed it must have been mined out after King's visit. In the pit, about 15 feet west of the shaft, approximately 150 pounds of zoisite and an occasiona1 small crystal of corundum were found imbedded in schist about 18 feet below the surface, near hard, dense troctolite."

Mar 1, 1946

By A. E. Raddatz

The Bureau of Mines has determined the electrochemical rate of anodic dissolution of vanadium metal in a VC12-VC13-NaC1 electrolyte at 860' C for the purpose of elucidating the reaction mechanism. Rate measurements were carried out with the help of specially designed equipment capable of continuously recording the weight loss experienced by a cylindrical vanadium anode immersed in the molten salt electrolyte while a constant current is maintained through it. The rate is expressed as a function of current density and VC13 concentration, and the reaction is interpreted in terms of an adsorption mechanism. Multiple regression analysis of the data gave the following rate equation: Rate x 104 (g.cm-2.sec-1) = -0.38 + 2.64 current density (amp-cm-2) + 0.69 log, (mole-percent VC13).

Jan 1, 1974

By J. M. Kuchta

The Bureau of Mines used laminar hot air jets of l/8- to 3/4-inch diam-eter to determine the hot gas ignition temperatures of various combustible vapor-air mixtures. The combustibles were n-hexane, n-octane, n-decane, a hydrocarbon jet fuel (JP-6), and an adipate ester aircraft engine oil (MIL-L- 7808). Minimum ignition temperatures occurred at a fuel to air weight ratio of about 0.5 and were not greatly sensitive to variations of fuel concentra¬tion. Moderate variations of jet velocity also had little influence on these ignition temperatures. However, these temperatures decreased with increase in heat source dimensions (jet diameter). The hot gas ignition temperatures of the combustibles were not necessarily much greater than corresponding autoignition and wire ignition temperatures when the size (,F the heat source and the ignition criterion were the same.

Jan 1, 1966

By M. M. Tilman

The Bureau of Mines conducted research to determine whether it is possible to substantially improve the fatigue resistance of lead sheet by means of surface coatings. Five types of coatings were applied to unalloyed chemical lead sheet. Flexural tests revealed that the best fatigue resistance was obtained with coatings of vacuum grease. Vacuum-grease coatings on unalloyed lead sheet resulted in fatigue resistance at least as good as that of the fatigue-resistant alloy Pb-0.04 Ca. Coated lead sheet was also tested in short-time tensile tests and in tensile creep tests. Tensile and yield strengths were increased by several of the coatings with only moderate loss of ductility. Creep resistance was also improved in varying degrees by most of the coatings. The Bureau also conducted research on the effectiveness of noise barriers by using sheet lead in combination with other materials. Noise barriers consisting of continuous-cast sheet lead with gypsum board were found to be effective and relatively inexpensive barriers.

Jan 1, 1978

By Michael S. Wieland

The work-principle method was developed for theoretically resolving toxic fumes from non-ideal charge formulations. The whole description of a wanted process refers to macroscopic changes resulting from removing and imposing constraints that work one at a time to chronologically render trajectory terminal (key) states. The trajectory resolution utilizes a thermodynamic quasi-potential or negative work function, and numeric results require some appropriate standard thermodynamic (equilibrium) reaction code TDRC. The underlying method is unable to restrict reactions, tailor the work output or resolve states within the trajectory transitions, so the trajectory terminology is used somewhat figuratively. The work-principle model has the working fluid (reaction material) interacting with a tremendous reservoir (chamber air and walls), while forecasting the work performed upon a mechanical agent. Within the underground test chamber, the widening fume zone undergoes a decline in temperature, a reduction in reaction rates, resulting in out-of- equilibrium circumstances at the Q*-point, representing the measurement state. Rather than coping with the hard issues of non-equilibrium, the toxic fumes are resolved numerically for the Z-point, rendered by a zero-net- interaction energy constraint. Though other techniques require complex equation-of-state EOS for the whole trajectory, the work-principle formulation eludes the issue, requiring an EOS that works just for the terminal-state. Under the circumstances, the Z-state is reconcilable with the ideal-gas domain, and relevant TDRC results yield the restricted state in a numerical way for different charge formulations. The work principle makes it hard to remedy or to tamper with the resulting Z-point fumes: non-macroscopic trajectory readjustment is forsaken, terminal states are results rather than stipulations, and resetting the EOS formula constants would be ineffectual. Though the non-equilibrium portion remains unresolved, it is noteworthy that the work principle rigidly fixes the Z-state, thereby reducing the uncertainty for rendering reaction-rate models characterizing the non-equilibrium Z-Q* transition. Though more refinements are needed, some Z-point fume results are included to illustrate the threshold (minimum) resolving capacity of the work- principle formulation.

By C. E. Jordan

Under its program of advancing minerals technology, the Federal Bureau of Mines has invented a laboratory apparatus for continuous separation of minerals based on differences in dielectric properties. The separator consists of a rotating drum electrode and a wire screen electrode positioned 3 mm apart. A high voltage applied across the electrodes that are immersed in a dielectric fluid produces a high-gradient electric field. The high-dielectric-constant (K) minerals are attracted to and conveyed through the separator by the rotating drum electrode, while the low K minerals settle through the screen electrode. Several design and operating parameters, such as electrode configurations, the dielectric liquid and its dielectric constant, electrical voltage and frequencies, feed rates, and particle sizes were studied. In addition, 28 different mineral mixtures were tested with the dielectric separator. In typical tests, a sample of rutile and quartz gangue containing 10-percent rutile was concentrated to 62-percent rutile with 94-percent rutile recovery. A second-stage dielectric separation of the rutile concentrate produced a 92-percent-rutile concentrate. The overall rutile recovery for the two-stage dielectric separation was 86 percent.

Jan 1, 1980

By E. L. Litchfield

Spark ignition of combustible-gas mixtures is a relatively old subject of investigation and has been treated both experimentally and analytically by many people. Elements of static and current electricity are almost always present in mining and industrial operations, and the spark can be an extremely efficient source of ignition. Thus the practical interest of such problems as the "intrinsic safety" of electrical apparatus is obvious. Ignition and quenching phenomena are the primary laboratory representatives of combustion phenomena that are dynamically nonsteady, and such nonsteady phenomena playa considerable part both in industrial processes and in safety matters, although they are of less immediate practical interest. Considerable effort has been expended by the Federal Bureau of Mines in investigations of spark ignition.5 6 7 8/ Primarily, this work has established the significance of several of the parameters involved. Although the

Jan 1, 1959

By Wing G. Agnew, John A. Johnson

"INTRODUCTION This paper is one of a series being published by the Bureau of Mines pertaining to an investigation on the use of stemming in metal mines now being conducted at the Mount Weather Testing Adit. Its purpose is to compare the amount of dust and gases produced as a result of blasting charges of dynamite (1) in drill holes, (2) in bombs, and (3) in mud-cap or adobe shots.ACKNOWLEDGMENTSValuable assistance and advice on stemming were given by members of the staff at the Bureau of Mines, as acknowledged in previous publications. 4/TEST PROCEDUREThe results used for comparison in this report are from dust and gas samples taken after blasting (1) four regular test rounds with no stemming, (2) five bomb shots, and (3) two mud-cap or adobe shots."

Dec 1, 1942

By J. M. Stuve

Low-temperature heat capacities of chiolite (Na5Al3F14) were determined by adiabatic calorimetry in the temperature range 5.8 to 300 K. The derived standard entropy (S°, 298.15) was 115.6 ± 0.2 cal/deg-mole. High temperature enthalpies relative to 298.15 K were obtained by precision drop calorimetry up to 1,000 K. Tables of experimental data and related thermodynamic functions are given for the temperature range of experimental observations.

Jan 1, 1980

By Geo S. Rice

"The most authoritative compilations on the coal resources of the British Isles are given in ""The Coal Resources of the World"" issued by the 12th International Geological Congress, 1913. The reserve, calculated to a depth of 6,000 feet, in seams containing not less than two feet of merchantable coal are as follows: Mining at present is conducted at depths from about 800 to 3500 feet. The shallower coals have largely been exhausted. The present average hoisting depth probably is about 1500 feet.The thickness of individual beds at present mined varies from about 2-1/2 feet up to 40 feet in thickness, the latter thickness being found in North Staffordshire. The coal is rarely found level, but is approximately level in some parts of Yorkshire. Anthracite is mined in limited quantities in Wales, and Wales also produces a very high grade semi-anthracite or smokeless coal, which is fa famous the world round, and is equaled only by the Pocahontas and New River coals in the United States:As concerns the methods of mining, these vary widely according to the pitch of the bed, the thickness of coal, and natural conditions, but the prevailing method is some form of longwall or semi-longwall, by which all the coal is extracted. The other principal method is a so-called pillar and, stall method, by which the coal is mined out, leaving square or rectangular pillars which are extracted on the retreat, making it virtually, a retreating longwall system. This method is applied where the roof is strong, and particularly in the thicker beds, as the longwall method is not so well adapted for mining where the thickness exceeds five or six feet, unless it is what is called a multiple seam, one in which there are partings of rock that provide material for building walls, which the roof in subsiding gradually squeezes down."

Jul 1, 1920

By Alex U. Miller

Since its beginning, the occupation of coal mining has been considered hazardous. It is true that there are hazards inherent in mining, but it is believed that most of them, at least, can be guarded against. Moreover, many man-made hazards can be eliminated by officials and workers adopting safer practices. Notwithstanding the hazards in coal mining, the fatal accident rate in the United States has improved. During the, period from 1911, to 1941, inclusive, the fatal accident rate varied from 5.35 to 2.22 per million tons of coal. With many handicaps during the war period, 1942-45, such as the lack of experienced manpower. and the, employment of untrained men, the increased average age of workers, and the shortage of equipment and supplies, the industry s ill further reduced its accident rate, so that it ranged from 2.30 to 1.724/ deaths per millon tons of coal. During 1944, 684,000,000 tons of coal was produced with a rate of 1.91, and during 1945, 631,000,000 tons was produced with a rate of 1.724/ deaths per millon tons of coal. The accident rate for 1945 was the lowest for the industry since records have been compiled.

Jan 1, 1946